By Marco Bello UVALDE, Texas (Reuters) -A gunman opened fire at an elementary school in South Texas on Tuesday, killing 14 children and one teacher, before the suspect himself died, Governor Greg Abbott told reporters, in the latest spasm of mass shootings sweeping the United States. Abbott said the suspect, identified as 18-year-old Salvador Ramos, apparently was killed by police officers responding to the scene, and that two of those officers were struck by gunfire, though the governor said their injuries were not serious. Authorities said the suspect acted alone. The latest episode of gun v…